How do I differentiate between benign and serious causes of rectal bleeding in adults?

To differentiate between benign and serious causes of rectal bleeding in adults, consider the following clinical features and risk factors:

• Age and symptom context: Adults aged 50 and over with unexplained rectal bleeding should be considered at higher risk for colorectal cancer and warrant further investigation, including quantitative faecal immunochemical testing (FIT) and possible urgent referral ¹,⁴.
• Associated symptoms suggesting serious pathology: Weight loss, abdominal pain, change in bowel habits, iron deficiency anaemia, or presence of a palpable rectal or abdominal mass increase suspicion of colorectal cancer or other serious conditions and require urgent referral ¹,⁴.
• Rectal bleeding in adults under 50: If accompanied by unexplained abdominal pain, change in bowel habits, weight loss, or iron-deficiency anaemia, this also warrants further assessment and possible referral ¹,⁴.
• Benign causes: Common benign causes include haemorrhoids and anal fissures, which typically present with bright red bleeding associated with defecation, often without systemic symptoms. Examination findings such as typical haemorrhoids or fissures support a benign diagnosis ²,³.
• Referral indications: Refer urgently via the suspected cancer pathway if there is unexplained rectal bleeding in those aged 50 and over, or if there is a rectal or abdominal mass, or if bleeding is accompanied by systemic features or anaemia ¹,⁴.

Summary: Rectal bleeding with systemic symptoms, anaemia, or in older adults is more likely to be serious and requires urgent investigation. Isolated bleeding with typical benign signs and no systemic features is more likely benign but still requires clinical assessment to exclude serious causes ¹,²,³,⁴.